The invention is concerned with the improvement of the filter in or for such an article by using platinum metal therein.
A certain amount of prior art exists on the use of transition metals in filters of smoking articles. Most of it stresses the alleged catalytic effect of the presence of such metals and has concentrated on presenting those metals in as active a form as possible.
Examples of this are seen in U.S. Pat. No. 4,317,460 and in a paper of the Research Laboratories of Eastman Chemical Products entitled "Results of Experimental Work to Remove carbon monoxide from a mixture of oxygen and nitrogen by Use of Modified Cigarette Filters", publication of which appears to have occurred in March 1978.
These publications were concentrating on the removal of carbon monoxide by catalytic oxidation. In U.S. Pat. No. 4,317,460 the supports used are microporous supports characteristic of catalysts, namely alumina or zeolites and the disclosure stresses the importance of distribution of the chosen metals throughout and within the support material, and also the importance of the generation of activated surfaces by the crushing of pre-impregnated pellets.
One of the metals mentioned is platinum but only in mixtures with other metals and especially in mixtures with rhodium, rhenium or tin. Such mixtures are intimate and as far as possible evenly distributed in the supports.
In the "Results of Experimental Work . . ." paper the author studied the effects of various oxidative catalysts including manganese dioxide and palladium. The study concluded that the carrier was a controlling factor and showed that platinum gave about the same results as palladium when borne on alumina but when borne on other materials no activity was observed.
In JP-B-82-011630 a cigarette filter has a layer of palladium or platinum supported on a composite of cement and powdered activated carbon and covered by second and third layers of respectively further activated carbon and an oxidant. This filter is said to remove carbon monoxide and oxides of nitrogen from cigarette smoke.
Thus the picture emerges of various elaborate and expensive suggestions for the catalytic manipulation of gaseous components of cigarette smoke in the filter by oxidation on transition metals.